Multiomics and blood-based biomarkers of electroconvulsive therapy in severe and treatment-resistant depression: study protocol of the DetECT study

Electroconvulsive therapy (ECT) is commonly used to treat treatment-resistant depression (TRD). However, our knowledge of the ECT-induced molecular mechanisms causing clinical improvement is limited. To address this issue, we developed the single-center, prospective observational DetECT study ("Multimodal Biomarkers of ECT in TRD"; registered 18/07/2022, www.clinicalTrials.gov , NCT05463562). Its objective is to identify molecular, psychological, socioeconomic, and clinical biomarkers of ECT response in TRD. We aim to recruit n = 134 patients in 3 years. Over the course of 12 biweekly ECT sessions (± 7 weeks), participant blood is collected before and 1 h after the first and seventh ECT and within 1 week after the twelfth session. In pilot subjects (first n = 10), additional blood draws are performed 3 and 6 h after the first ECT session to determine the optimal post-ECT blood draw interval. In blood samples, multiomic analyses are performed focusing on genotyping, epigenetics, RNA sequencing, neuron-derived exosomes, purines, and immunometabolics. To determine clinical response and side effects, participants are asked weekly to complete four standardized self-rating questionnaires on depressive and somatic symptoms. Additionally, clinician ratings are obtained three times (weeks 1, 4, and 7) within structured clinical interviews. Medical and sociodemographic data are extracted from patient records. The multimodal data collected are used to perform the conventional statistics as well as mixed linear modeling to identify clusters that link biobehavioural measures to ECT response. The DetECT study can provide important insight into the complex mechanisms of ECT in TRD and a step toward biologically informed and data-driven-based ECT biomarkers.

The P2X7 receptor in mood disorders: Emerging target in immunopsychiatry, from bench to bedside

Psychiatric disorders are among the most burdensome disorders worldwide. Though therapies have evolved over the last decades, treatment resistance still affects many patients. Recently, neuroimmune systems have been identified as important factors of mood disorder biology. The underlying dysregulation in neuroimmune cross-talk is driven by genetic risk factors and accumulating adverse environmental influences like chronic psychosocial stress. These result in a cluster of proinflammatory cytokines and quantitative and functional changes of immune cell populations (e.g., microglia, monocytes, T cells), varying by disease entity and state. Among the emerging immune targets, purinergic signalling revolving around the membranous and ATP specific P2X7 receptor (P2X7R) has gained wider attention and clinical studies making use of antagonistic drugs are on-going. Still, no clinically meaningful applications have been identified so far. A major problem is the often overly simplified approach taken to translate findings from bench to bedside. Therefore, the present review focuses on purinergic signalling via P2X7R in the context of recent advances in immunopsychiatric mood disorder research. Our aim is to provide an overview of the current P2X7R-related findings, from bench to bedside. First, we summarize the characteristics of purinergic signalling and P2X7R, followed by a depiction of genetic and clinical data connecting P2X7R to mood disorders. We close with our perspective on current developments and discuss changes necessary to translate the evident potential of P2X7R signalling modulation into meaningful clinical application. This article is part of the Special Issue on 'Purinergic Signaling: 50 years'.

Introducing a depression-like syndrome for translational neuropsychiatry: a plea for taxonomical validity and improved comparability between humans and mice

Depressive disorders are the most burdensome psychiatric disorders worldwide. Although huge efforts have been made to advance treatment, outcomes remain unsatisfactory. Many factors contribute to this gridlock including suboptimal animal models. Especially limited study comparability and replicability due to imprecise terminology concerning depressive-like states are major problems. To overcome these issues, new approaches are needed. Here, we introduce a taxonomical concept for modelling depression in laboratory mice, which we call depression-like syndrome (DLS). It hinges on growing evidence suggesting that mice possess advanced socioemotional abilities and can display non-random symptom patterns indicative of an evolutionary conserved disorder-like phenotype. The DLS approach uses a combined heuristic method based on clinical depression criteria and the Research Domain Criteria to provide a biobehavioural reference syndrome for preclinical rodent models of depression. The DLS criteria are based on available, species-specific evidence and are as follows: (I) minimum duration of phenotype, (II) significant sociofunctional impairment, (III) core biological features, (IV) necessary depressive-like symptoms. To assess DLS presence and severity, we have designed an algorithm to ensure statistical and biological relevance of findings. The algorithm uses a minimum combined threshold for statistical significance and effect size (p value ≤ 0.05 plus moderate effect size) for each DLS criterion. Taken together, the DLS is a novel, biologically founded, and species-specific minimum threshold approach. Its long-term objective is to gradually develop into an inter-model validation standard and microframework to improve phenotyping methodology in translational research.

The human P2X7 receptor alters microglial morphology and cytokine secretion following immunomodulation

Introduction: In recent years, purinergic signaling via the P2X7 receptor (P2X7R) on microglia has repeatedly been implicated in depression genesis. However, it remains unclear which role the human P2X7R (hP2X7R) plays in regulating both microglia morphology and cytokine secretion upon different environmental and immune stimuli, respectively. Methods: For this purpose, we used primary microglial cultures derived from a humanized microglia-specific conditional P2X7R knockout mouse line to emulate different gene-environment interactions between microglial hP2X7R and molecular proxies of psychosocial and pathogen-derived immune stimuli. Microglial cultures were subjected to treatments with the agonists 2'(3')-O-(4-benzoylbenzoyl)-ATP (BzATP) and lipopolysaccharides (LPS) combined with specific P2X7R antagonists (JNJ-47965567, A-804598). Results: Morphotyping revealed overall high baseline activation due to the in vitro conditions. Both BzATP and LPS + BzATP treatment increased round/ameboid microglia and decreased polarized and ramified morphotypes. This effect was stronger in hP2X7R-proficient (CTRL) compared to knockout (KO) microglia. Aptly, we found antagonism with JNJ-4796556 and A-804598 to reduce round/ameboid microglia and increase complex morphologies only in CTRL but not KO microglia. Single cell shape descriptor analysis confirmed the morphotyping results. Compared to KO microglia, hP2X7R-targeted stimulation in CTRLs led to a more pronounced increase in microglial roundness and circularity along with an overall higher decrease in aspect ratio and shape complexity. JNJ-4796556 and A-804598, on the other hand, led to opposite dynamics. In KO microglia, similar trends were observed, yet the magnitude of responses was much smaller. Parallel assessment of 10 cytokines demonstrated the proinflammatory properties of hP2X7R. Following LPS + BzATP stimulation, IL-1β, IL-6, and TNFα levels were found to be higher and IL-4 levels lower in CTRL than in KO cultures. Vice versa, hP2X7R antagonists reduced proinflammatory cytokine levels and increased IL-4 secretion. Discussion: Taken together, our results help disentangle the complex function of microglial hP2X7R downstream of various immune stimuli. In addition, this is the first study in a humanized, microglia-specific in vitro model identifying a so far unknown potential link between microglial hP2X7R function and IL-27 levels.

P2X7 Receptor-Related Genetic Mouse Models – Tools for Translational Research in Psychiatry

Depression is a common psychiatric disorder and the leading cause of disability worldwide. Although treatments are available, only about 60% of treated patients experience a significant improvement in disease symptoms. Numerous clinical and rodent studies have identified the purinergic P2X7 receptor (P2X7R) as one of the genetic factors potentially contributing to the disease risk. In this respect, genetically engineered mouse models targeting the P2X7R have become increasingly important in studying designated immunological features and subtypes of depression in vivo. This review provides an overview of the P2X7R -related mouse lines currently available for translational psychiatric research and discusses their strengths, weaknesses, and potentials.

Combined Fainting and Psychogenic Non-epileptic Seizures as Significant Therapy Hurdles in Blood-Injury-Injection Phobia: A Mini-Review and Case Report

BACKGROUND

Anxiety disorders are the most frequent mental disorders. Among the different subtypes, specific phobias are the commonest. Due to the ongoing SARS-CoV-19 pandemic, blood-injury-injection phobia (BII) has gained wider attention in the context of large-scale vaccination campaigns and public health. In this BII phobia mini-review and case report, we describe the successful treatment of a severe BII phobia case with combined fainting and psychogenic non-epileptic seizures (PNES) and demonstrate the role of specialized outpatient care.

CASE REPORT

The patient was a 28-year-old woman. She suffered from intense fear and recurrent fainting with regard to needles, injections, injuries, and at the sight of blood since early childhood. Medical history revealed infrequent events suggestive of PNES following panic attacks after sustained exposure to phobic stimuli. Family history was positive for circulation problems and BII fears. Psychopathological evaluation confirmed BII phobia symptoms and diagnosis was made according to the DSM-5. The Multidimensional Blood/Injury Phobia Inventory short version (MBPI-K) revealed severe manifestation of the disease. Neurological examination was ordinary. Repeated electroencephalography detected no epileptic pattern. Cranial magnetic resonance imaging showed normal morphology. Treatment was carried out by a seasoned, multidisciplinary team. Cognitive behavior therapy and exposure were performed. Modification of standard treatment protocol was necessary due to hurdles posed by recurrent fainting and a severe panic-triggered dissociative PNES during in vivo exposure. Modification was implemented by limiting in vivo exposure intensity to moderate anxiety levels. In addition to applied muscle tension and ventilation techniques, increased psychoeducation, cognitive restructuring, and distress tolerance skills (e.g., ice pack, verbal self-instructions) were used to strengthen the patient's situational control during in vivo exposure. A total of 15 sessions were performed. Therapy success was proven by 83% reduction in MBPI-K rating, SARS-CoV-19 vaccination, and a blood draw without psychological assistance, fainting, or seizure.

CONCLUSION

Taken together, this case demonstrates the potential of and need for specialized outpatient care and individualized treatment for severe BII phobia patients in order to provide them the perspective to have necessary medical procedures done and get vaccinated.

In vivo two-photon characterization of tumor-associated macrophages and microglia (TAM/M) and CX3CR1 during different steps of brain metastasis formation from lung cancer

Brain metastases frequently occur in lung cancer and dramatically limit prognosis of affected patients. The influence of tumor-associated macrophages and microglia (TAM/M) and their receptor CX3CR1 on different steps of brain metastasis formation from lung cancer is poorly characterized. We established a syngeneic orthotopic cerebral metastasis model in mice by combining a chronic cranial window with repetitive intravital 2-photon laser scanning microscopy. This allowed in vivo tracking of fluorescence-expressing tumor cells and TAM/M on a single-cell level over weeks. Intracarotid injection of red tdTomato-fluorescent Lewis lung carcinoma cell was performed in transgenic mice either proficient or deficient for CX3CR1. After intracarotid cell injection, intravascular tumor cells extravasated into the brain parenchyma and formed micro- and mature macrometastases. We observed potential phagocytosis of extravasated tumor cells by TAM/M. However, during later steps of metastasis formation, these anti-tumor effects diminished and were paralleled by TAM/M accumulation and activation. Although CX3CR1 deficiency resulted in a lower number of extravasated tumor cells, progression of these extravasated cells into micro metastases was more efficient. Overall, this resulted in a comparable number of mature macrometastases in CX3CR1-deficient and -proficient mice. Our findings indicate that unspecific inhibition of CX3CR1 might not be a suitable therapeutic option to prevent dissemination of lung cancer cells to the brain. Given the close interaction between TAM/M and tumor cells during metastasis formation, other therapeutic approaches targeting TAM/M function may warrant further evaluation. The herein established orthotopic mouse model may be a useful tool to evaluate such concepts in vivo.

BSCI-08. In vivo two-photon characterization of tumor-associated macrophages and microglia (TAM/M) and CX3CR1 during different steps of brain metastasis formation from lung cancer

Background

Brain metastases represent a common complication of lung cancer and dramatically limit prognosis in affected patients. The influence of tumor-associated macrophages and microglia (TAM/M) and their receptor CX3CR1 on different steps of brain metastasis formation from lung cancer is poorly characterized, but might be of therapeutic relevance.

Methods

We established an orthotopic cerebral metastasis model using CX3CR1-proficient (CX3CR1GFP/wt) and -deficient (CX3CR1GFP/GFP) mice with green-fluorescent TAM/M. A cranial window was prepared, and intracarotid injection of red-fluorescent Lewis Lung Carcinoma-cells (tdtLLC) was performed two weeks later. Formation of brain metastases was followed by repetitive two-photon laser scanning microscopy.

Results

After intracarotid injection, intravascular tumor cells extravasated into the cerebral parenchyma and eventually formed micrometastases (≤50 cells) and mature macrometastases (>50 cells). We observed phagocytosis of extravasated tumor cells by TAM/M during early steps of metastatic growth. Notably, these anti-tumor effects of TAM/M diminished during later steps of metastasis formation and were accompanied by TAM/M accumulation and activation. CX3CR1-deficiency resulted in a lower number of extravasated tumor cells, and only a small number of TAM/M were visualized during early steps of metastasis formation (extravasation, formation of micrometastases) in such mice. In contrast, progression of extravasated tumor cells into micrometastases was more frequently found in CX3CR1-deficient mice. Overall, these mechanisms resulted in a comparable number of mature macrometastases between CX3CR1-deficient and -proficient mice.

Conclusion

Our findings indicate that unspecific inhibition of CX3CR1 might not be a suitable therapeutic approach to prevent cerebral dissemination of lung cancer cells. Given the close interaction between TAM/M and tumour cells during metastasis formation, other therapeutic approaches targeting TAM/M function warrant evaluation. Such concepts might be evaluated in vivo using the herein established orthotopic mouse model.

TAMI-02. ALTERATIONS IN C-X3-C MOTIF CHEMOKINE RECEPTOR 1 (CX3CR1) EXPRESSION INFLUENCE MICROGLIAL AND MACROPHAGE RESPONSE IN DIFFERENT STEPS OF CEREBRAL METASTASIS FORMATION

Metastasis to the brain is a frequent complication in lung cancer and is still associated with a dismal prognosis. Current treatment strategies not only target tumor cells but also focus on cells of the tumor microenvironment like tumor associated microglia/macrophages (TAMs). The interactions between tumor cells and TAMs during different steps of cerebral metastasis formation of lung cancer brain metastasis are poorly characterized. Moreover, the role of CX3CR1 in this process remains unclear. We established a syngeneic cerebral metastasis mouse model by combining a chronic cranial window and two-photon laser scanning microscopy (TPLSM), which allows the tracking of single fluorescent metastasizing tumor cells and the tumor microenvironment on a cellular resolution in vivoover time for a period of weeks. Transgenic CX3CR1 proficient and deficient mice (CX3CRGFP/wt and CX3CR1GFP/GFP) were injected with red fluorescent Lewis lung carcinoma cells. During different steps of metastasis formation (extravasation, formation of micro- and macrometastasis) the density and cell body volume of TAMs, their interaction with tumor cells and possible influence on the fate of single metastatic tumor cells were investigated using serial TPLSM. We found that during metastasis formation TAM density was significantly lower in CX3CR1 deficient mice. However, activation as assessed by TAM morphology did not differ in the absence of CX3CR1. Strikingly, CX3CR1 deficiency was associated with a significant increase of tumor cells successfully extravasating the cerebral vasculature. However, subsequent steps (mirco- and macrometastasis formation) were observed less frequent in CX3CR1 deficient mice. In summary, our results highlight a complex role of CX3CR1 for TAMs during cerebral metastasis formation, indicating anti-tumorous properties of CX3CR1 at early steps and possible pro-tumorous effects at later stages (micro- and macrometastasis formation).

The Role of BAFF-R Signaling in the Growth of Primary Central Nervous System Lymphoma

Primary CNS lymphoma (PCNSL) is an aggressive brain tumor. Despite improvements in therapeutic algorithms, long-term survival remains rare, illustrating an urgent need for novel therapeutic targets. BAFF-R is a pro-survival receptor expressed on most malignant B cells, including PCNSL. To date, its role in PCNSL growth remains elusive. Here, we have created a BAFF-R knockout lymphoma cell line (BAFF-R-KO) using CRISPR-Cas9. In serum-starved conditions, BAFF-R-KO cells exhibit decreased viability in vitro compared to BAFF-R⁺ cells. Combining an orthotopic mouse model of PCNSL with chronic cranial windows and intravital microscopy, we have demonstrated a significant delay in tumor growth in mice inoculated with BAFF-R-KO cells compared to BAFF-R⁺ PCNSL. Additionally, median survival of BAFF-R-KO mice was significantly prolonged. Altogether, our results indicate the high potential of BAFF-R as a novel treatment target for PCNSL.